-: Okay, as far as the quadriceps go,
we have a group of muscles all here
that as a group create full knee extension.
Okay.
And we're gonna start off from the medial side.
We're gonna talk about the what's called the VMO
or the vastus medialis obliques,
which from a medial standpoint
attaches right into the middle portion of the femur
and wraps all the way around
and then starts to fuse with this common tendon here
that attaches into this tibial tuberosity.
Now all the quadriceps from the top come down
and they all fuse together over this patella tendon
and tie right into this tibial tuberosity.
So if we look at that here,
there's a little bump on the front of the leg
and this is where all those quadriceps insert.
This one's a little bit deceiving
because this patella,
which looks like it's just floating up here,
but they all wrap around
and kind of fuse with this kind of bone here
and use it as like a little lever to get a better angle
from which to do this motion with.
Moving along to the middle portion here.
We've got this blue line,
which represents the rectus femoris,
which we'll talk about in a second,
but deep to that we have this orange thing
that kind of comes around and spreads apart.
And this attaches directly to the top of the femur
and it's called the vastus intermedius.
Okay, which is a lot of times we cannot see this muscle
just because it's sitting so deep underneath.
And then towards the outside,
this large purple guy here
that covers most of the lateral portion of the leg
is called the vastus lateralis.
And again, this attaches up to the upper portions
of the femur all the way underneath even
towards the posterior side
and comes around and infuses together
with that same tendon here.
And the last guy,
actually the last two guys that we'll talk about,
there is a brand new muscle that was discovered
in was it 2016, I believe
where they did some cadaver dissections
and found that this muscle here existed
in all 26 of the cadavers.
And this is called your tensor vastus intermedius,
which kind of sits interior to the TFL.
And it fuses with the intermedius
and actually adds another kind of like pull laterally
to help stabilize that patella tendon.
And it's tracking back and forth
as the knee extends and flexes.
And the last guy here,
which is one of the more important ones
is going to be the rectus femoris,
which comes all the way across.
And it's the only biarticular muscle that we have
as far as the knee extensors go.
So this one attaches directly to the hip,
to the a AIIS or the anterior inferior iliac spine
and also ties right into the neck of the femur.
And then again, crosses that common tendon
all the way across into that to tuberosity.
On the other side
we have one other conditional knee extensor,
which can actually be a knee flexor
depending on where that knee sits in space.
We've got something called the sartorius,
which crosses the knee this way.
And if we were to actually see this thing short and fully,
it would create kind of like a external rotation,
hip flexion, knee flex type situation.
But depending on how much knee extension
or how far in knee extension they are,
or if they even hyper-extend in some cases,
this will have a synergistic impact
with the rest of the quadriceps
to help to guide and complete that knee extension.
So depending on what the body needs,
where it needs some extra support
it can actually be very helpful
for a knee extension function,
or it can be helpful for the completion of a knee flex.
-: When we look at the function of the quads,
they're all going to share the quality of knee extension.
However, the rectus femoris actually comes up
and attaches at the hip.
So it is also going to be a hip flexor
and therefore it's length is going to be subject
by changing the orientation of the hip.
As you do those exercises,
it's also going to function similar to the hamstring
in two joint exercises such as squats and presses,
where it will be shortening at the hip
and lengthening at the knee,
and then vice versa as you're going through
that stretch shortening cycle of a two joint
like pressing lower body motion, hack squat, lunge,
split squat, you name it.
Anytime that we are going this way
while bending the knee,
we're going to get kind of more of an isometric contraction
out of that rectus femoris.
And it's going to be communicating length tension wise
with that hamstring and kind of help manage
that pelvis position.
So it's really going to function
as a pelvis stabilizer in those compound movements
and kind of giving permission on how the joint can move
and where tension needs to be placed
in terms of the other muscles around the joint.
So hamstrings and rec fem have a very intimate relationship
in terms of managing stability of this hip
and stability of the knee joint as well.
The rest of the quads, they're going to just function
as knee extensors, but they're still going to vary
in terms of their mechanics at different lengths.
So if we look at these, we have very different shapes
in terms of the muscle bellies, both in length and in width.
So that kind of matches.
We have internal mechanics
and external mechanics here that are gonna vary.
And what that means is like for muscles
that have multiple bellies
such as the hamstrings and the quads,
you need to train them with more resistance profiles
and kind of through a variety of ranges of motion.
So even though you know, the quadriceps here,
most of them outside of the rec fem
are only going to be affected
by bending the knee in terms of training,
it still will benefit us to load them
at different points of that.
So if we look at all of our pressing based exercises
like hack squats, squats, lunges, split squats,
we tend to be loading that lengthened position.
So being able to incorporate and exercise
like a leg extension
that's gonna load that fully shortened position
really fills in a gap and a need
for full quadricep development.
And then trying to use things
like accommodating resistance or using a torque arm
or a smart cam to be able to load the mid-range position
or maybe even partial reps can be very valuable
for fully developing the quad.
Now, the other thing to consider
with this rec fem is also understanding
that similar to hip extension in a leg curl,
hip flexion in a knee extension exercise
can affect this rec fem's ability to add tension
or add the mechanical work to that leg extension
or knee extension movement.
So if you were to get to the point
where you reached like a-
Or get to the point where the rec fem
was maximally shortened and there was too much stretch
on the hamstring,
you could get to the point
where it could no longer help continue
to get into the short position,
which could decrease stability here,
could decrease stability at the knee,
and you can get to the point then
where like the recruitment of those other quads
is going to change because the rec fem
is going to pass you know, like passively be inhibited
and therefore the other stuff's
either gonna have to make up for that
or you'll see a range of motion change.
Ideally we want to train
when we have all of this stuff functioning properly
because it gives us the most stable joints,
therefore the best ability to get force output
and maximum tension within those muscles.
We don't want to be limited by stability
because then we're just gonna be less likely
to get to the training stimulus
in as much volume or as much repetitions that we want.
We're gonna end up having to do more
to get the same stimulus
if we're even able to achieve it at all.
It's better to try and maximize the you know,
the output of those tissues by maximizing the stability
and working within the range
that the joint's naturally meant to function.